Heat exchanger



Nov. 16, 1965 P. N. RENZI 3,217,798 1 HEAT EXCHANGER Filed Dec. 5, 1962 2 Sheets-Sheet l x a Q A' u a s m g Q LO Q h U N x Q Q [x INVENTOR Peter N. Renzi Fig. 2.

ATTORNEY P. N. RENZI HEAT EXCHANGER Nov. 16, 1965 2 Sheets-Sheet 2 Filed Dec. 5, 1962 INVENTOR Peter N. Renzi BY W ATTORNEY Fig. 7.

United States Patent 3,217,798 HEAT EXCHANGER Peter N. Renzi, Mountainside, N.J., assignor to American Radiator & Standard Sanitary Corporation, New York, N.Y., a corporation of Delaware Filed Dec. 5, 1962, Ser. No. 242,507 Claims. (Cl. 165-152) This invention relates to a heat exchanger and to a method of making a heat exchanger of the type in which fluids are maintained separated from one another as they pass therethrough. The principles of the invention may, for example, be adapted for use in a heat exchanger of the type wherein a fluid is made to flow over tubes which are in contact with heat transfer fins while a second fluid, exchanging heat with the first fluid, is made to pass through the tubes.

Heretofore, heat exchangers of this last mentioned type have been made, in one known method, by stamping pieces of sheet metal wherein holes are pierced in the sheet metal so that the sheet metal could be slipped over heat exchange tubes. Subsequently, U-shaped return bends were soldered or welded to connect one heat exchange tube row with the next so as to form a continuous coil. The disadvantage of this method was that the heat exchange tubes had to be initially made in separate straight lengths and return bends or U-shaped sections subsequently soldered or welded at the ends thereof to provide a continuous flow path. The necessity of having to solder or weld these return bends obviously increased the time and cost of manufacture of these types of heat exchangers.

In other known types of heat exchangers the fins between heat exchanger tubes have been made of complicated and intricate designs which increase the cost of manufacture and the total amount of fin material used but did not always provide the best possible heat transfer efficiency.

The present invention overcomes the difliculties of prior art devices by utilizing a preformed cellular structure, such as in the form of a honeycomb for example, arranged in staggered array wherein sections of such cellular structure are placed between the heat exchanger tubes or coils in such a way as to provide a firm contact therebetween so that the cellular structure serves as heat exchange fins. Such sections of cellular structure may, for example, be placed between the heat exchange tubes after the tubes have been formed into coils or continuous flow paths thereby making it possible, in the case of the heretofore mentioned coil type of heat exchanger, to form the return bends of the heat exchanger tubes integral with the straight length portions thereof.

It has also been found that the highest degree of heat transfer occurs at the leading edges of heat transfer fins, that is the edges which are initially contacted by the fluid medium passing through the fin arrangement. Thus the staggered arrangement of the cellular fin structure of the present invention provides a relatively large number of leading edges functioning as heat transfer fins for maximum heat transfer efficiency.

Accordingly, it is an object of the present invention to provide a heat exchanger which is inexpensive to construct and which has a high heat transfer efliciency.

Another object is to provide a heat exchanger having heat exchange fins with a relative large number of leading edges and which requires less total fin surface than prior known heat exchangers.

Another object is to provide a method for making a heat exchanger having a fin structure which may be installed between preformed heat exchanger coils.

Another object is to provide a heat exchanger having 3,217,798 Patented Nov. 16, 1965 coils or tubes arranged in serpentine fashion and having integrally formed return bends and a fin structure in intimate contact with the external surfaces of the tubes to facilitate heat transfer.

Another object is to provide a heat exchanger which can be manufactured Without requiring soldering or welding of return bends.

Another object is to provide a heat exchanger which requires less fin material than that of prior known heat exchangers.

Another object is to provide a heat exchanger having lanes or passageways in the fin structure for conducting condensate resulting from cooling of gaseous fluids passing by the fin surfaces.

Another object is to provide a heat exchanger having a fin structure coated at least partially with a wetting agent to facilitate condensate run-off.

Another object is to provide a heat exchanger in which the condensate blow-off is avoided.

Other objects and features of the invention will appear as the description of the particular physical embodiment selected to illustrate the invention progresses.

For a better understanding of the present invention reference should be had to the accompanying drawings wherein like numerals of reference indicate similar parts throughout the several views and wherein:

FIGURE 1 is a schematic view representing a partial side elevation of a heat exchanger showing heat exchanger coils and fin structures arranged according to one embodiment of the invention.

FIGURE 2 is a sectional view taken along the lines 22 of FIGURE 1 looking in the direction of the arrows.

FIGURE 3 is a schematic view of one section of fin structure used in the heat exchanger of FIGURES 1 and 2.

FIGURE 4 is a schematic view similar to FIGURE 1 but showing a modified fin structure arrangement.

FIGURE 5 is a sectional view taken along the line 55 of FIGURE 4 looking in the direction of the arrows.

FIGURE 6 is a partial schematic view, similar to FIG- URE 1, but showing means for holding the fin structure in the heat exchanger against the heat exchanger tubes.

FIGURE 7 is a partial schematic view, similar to FIG- URE 5, but showing a modified means for securing the fin structure in the heat exchanger and against the heat exchanger tubes.

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed is for the purpose of description and not of limitation.

Referring to FIGURE 1 a heat exchanger is shown schematically as comprising a heat exchange conduit 9 arranged in conventional serpentine fashion as a coil 10. The heat exchange conduit 9 may have a circular, oval, or other suitable cross-sectional configuration. As can best be seen in FIGURE 2 a plurality of such coils 10, 12, 14 are shown arranged in generally vertical planes or columns with the straight length portions of adjacent coils staggered in a conventional manner to provide maximum exposure and resulting in increased heat transfer efficiency. These coils 10, 12, 14 conduct a fluid medium which is to receive or give up heat while the area external of such tubes is exposed to a flow of another fluid medium which is also to receive or give up heat, such fluids being in heat exchanging relationship with one another.

For the purposes of this explanation it will be assumed that water flows through the coils 10, 12, 14, while air flows past the external surfaces of the coils to cool the water flowing therethrough. It is to be understood, however, that any other suitable fluid mediums may be used as desired. Suitable means may be provided for causing the water and air to flow through the heat exchanger such as a pump and fan respectively (not shown).

Each heat exchange coil 10, 12, 14 may be formed from a single tube 9 merely by forming therein successive return bends, such as the N-shaped return bend 16 shown in FIGURE 1. Each coil 10, 12, 14 may terminate in headers (not shown) or they may be connected serially by providing the necessary return bends between adjacent coils 10, 12 and 14. The complete array of coils 10, 12 and 14 may be made from a single tube without requiring any soldering or welding of return bends. However, for the sake of convenience, individual sections of the heat exchanger tube may be formed separately and subsequently soldered or welded together particularly in cases where the size or length of the initial unformed heat exchange tube would be excessive or the formed heat exchange tube would be bulky, but in any event it would not be necessary to solder or weld each individual return bend.

The heat exchanger may be assembled by placing between or adjacent the coils 10, 12, 14 individual sections 18, 20, 22, 24 of a cellular type of material or structure, such as a honeycomb structure made of a suitable material having good heat conducting properties, such as copper or aluminum for example.

Each section 18, 20, 22, 24 of cellular structure may be provided with cut-outs or notches such as at 26 corresponding to one-half or almost one-half the configuration or circumference of a cross-section of the heat exchange tubes defining the sides of the rows in which such sections 18, 20, 22, 24 are to be placed. One section of cellular structure 18 is shown in FIGURE 3 in the form of a honeycomb having wall members such as at 28 defining a plurality of adjacently arranged semi-enclosed cells or conduits such as at 30. Honeycomb structure is wellknown and requires no further description. The air flows through the cells or conduits 30 of the honeycomb structure generally parallel to the walls defining such cells or conduits. Each cell 30 is shown as being a hexagon but it is to be understood that the cellular structure may have a more or less number of sides which may be either straight or arcuate.

The notches 26 are provided on opposite edge portions on alternate rows of cells 30 to engage respectively, portions of the heat exchange tubes which make up the coils.

One method of assemblying the heat exchanger may comprise placing one coil (the coil 11) for example) adjacent the section of cellular structure 24 so that the notches 26 engage the straight length portions of the tubes of the coil 10, then placing the section of cellular structure 22 on an opposite side of the coil while engaging the notches therebetween, placing the next coil 12 in the notches of the section of cellular structure 12 and continuing in this manner to complete the assembly.

As an alternate method of construction, the notches 26 may be dispensed with and the cellular structure made of a thickness corresponding to the distance between adjacent coils so that the cellular structures may be inserted between the coils 10, 12, 14, by sliding each section in from one end (the right hand end of FIGURE 1, for example) and parallel to the general plane of the coils. The assembly thus formed may then be compressed, by means to be described, hereinafter, so that the end walls of the cellular structure will be crimped or bent by the tubes of the coil, thus the notches will be formed as the unit is assembled.

As a further alternative method of construction the individual coils may be connected serially to one another by interconnecting return bends and sections of notched cellular structure inserted between the coils by bending the interconnecting return bends to further separate the coils so that the cellular structure can be received between the 4 coils and then re-bending the interconnecting bends back to their original position.

Returning to the description pertaining to the embodiment of FIGURES l to 3, as each section of cellular structure 18, 20, 22, 24 is placed adjacent the coils 10, 12, 14, the notches 26 engages the sides of the straight length portions of the tubes of the coils while edge portions of the sections of cellular structure pass between the straight length tube portions of the individual coils. The size of each section of cellular structure may correspond to approximately the overall outline of the heat exchanger or if deemed suitable, such as in the case of larger size units, each section of cellular structure may be made of several individual pieces.

Adjacent sections of cellular structure may be arranged and constructed so that they are spaced from one another within the heat exchanger. For example, the numeral 32 in FIGURE 2 indicates the space between the cellular structure sections 21 and 22. The spaces between the sections of cellular structure provide a lane through which condensate, which may result from air cooling, may flow.

To facilitate condensate run-off resulting, for example, from moisture condensation in the air flowing through the cells, the edges of the sections of cellular structures may be provided with a wetting agent. A wetting agent on the downstream or on both the downstream and upstream edges of the cellular structure may be used, for example, to facilitate condensate run-off for coils operating with dehumidification and where air velocities are so high that condensate blow-off would occur if this special precaution were not taken. The numeral 31 in FIGURE 3 indicates, for example, a wetting agent along the edges of cell 30'.

As the condensate drains from each cell, it will flow around the heat exchange tubes and between the spaced cellular structures to provide vertical drainage thereof. One example of a wetting agent which can be used for this purpose is Resorcinal, a type of adhesive used in plasticizers, dyes, and for adhesion purposes. This wetting agent will not dissolve in water and is more readily wettable by water than a metal surface. Alternatively, instead of providing a wetting agent to the surfaces of the cells, the edges of the cells may be roughened to provide surface imperfections therein, such imperfections serving to provide a more wettable surface to facilitate condensate run-off.

Adjacent sections of cellular structure may be offset or staggered relative to one another, as shown in FIGURE 1, so that individual cells in each section are precluded from aligning with one another to avoid large uninterrupted channels for the air passing therethrough. With such an offset arrangement, higher heat transfer rates are realized necessitating substantially less heat transfer surface than in the case where conventional plane uninterrupted passages is used.

In the embodiment of FIGURES 1-3, the cellular structure is arranged such that a side wall of each cell has a length substantially equal to the diameter of the heat exchange tube while the distance between individual straight length tube portions of a coil is substantially equal to the maximum height or width of each cell. With such a cellular structure arranged within the heat exchanger such that the cells have side walls extending perpendicular to the longitudinal axis of the straight length portions of the heat exchange tubes, the notches 26 in each cellular structure section may be located in the opposed edge portion of the cell walls along alternate rows of cells as shown in FIGURE 3.

In the embodiment of FIGURES 4 and 5 the perpendicular distance between opposite side walls of a cell (one cell is indicated at 30a) is substantially equal to the distance between the centerlines of individual straight length tube portions of the coils 10b, 12b, 14b, and the cellular structures 18b, 20b, 22b, 24b are arranged in the heat exchanger such that each cell has side walls parallel to the longitudinal axis of the straight line portions of the tubes.

The coils b, 12b, 14b in the embodiment of FIG URES 4 and 5 are arranged similarly to the arrangement in the embodiment of FIGURES 1-3. The size and arrangement of the cellular structure in the heat exchanger may be varied as desired, the arrangement of FIGURES 1 and 4 merely representing two examples.

The cellular sections contact the tubes of the coils along the notches 26 to facilitate heat transfer between the tubes and the walls of the cellular structure. Suitable means may be provided to secure the cellular sections in the heat exchanger and to insure that firm contact is maintained between the tubes and the notches.

Such means may comprise welding or brazing 34 (FIG- URE 6) between the tubes of coils 12a, 14a and the notches of the cellular structures 18a, 20a, 22a.

In an alternative embodiment shown in FIGURE 7, contact members or straps 36 and 38 may be provided on either end of the heat exchanger while stay belts 40 and 42 extending between the ends of the heat exchanger may be used to urge the straps 36, 38 towards one another thereby tending to urge the sections of cellular structure towards one another. For this purpose the ends of the stay belts 40 and 42 may be provided with threads for engaging the nuts 44 and 46 respectively. As the nuts on the stay belts are tightened, the tendency of the cellular structures to be urged towards one another will be arrested by the engagement between the tubes and the notches 26 of the cellular structures to provide a firm contact therebetween. If the coils are made of conventional materials usually used for this purpose, the coils may flex slightly as the sections of cellular structure are urged toward one another, due to the resiliency of the coils. Thus firm contact between all the tubes and sec tions of cellular structure is assured.

Although the straight length portions of the coils are shown as extending generally horizontally in the drawings, they may also be arranged to extend vertically or at some intermediate angle as desired.

With the staggered arrangement of alternate sections of cellular structure, as previously set forth, there will be a high heat transfer efliciency because of the greater number of leading edges presented to the air flowing through the heat exchanger. It is believed evident from the drawings and from the above description that, as the air passes through and exits from an individual cell of one cellular structure section, it will encounter a plurality of leading edges of the cells of the next adjacently arranged and staggered cellular structure section. As can be clearly seen in FIGURES 4 and 5, for example, as the air leaves the cell 30:: it immediately encounters the leading edges 33, 35 and 37 of cells in the adjacent cellular structure.

With this arrangement there will be a high heat transfer because of the greater number of leading edges presented to the gas flow.

From the above description it will be evident that the heat exchanger of the present invention will have a high heat transfer etficiency due to the relative large number of leading edges on the fin structure thereby making it possible to reduce the total amount of fin material. The cellular structural sections may be placed between the coils of a heat exchanger after such coils have been preformed into a continuous passageway thereby making it possible to form the coil from a single tube or from large lengths of tubes. A firm contact between the cellular structures and the coils assures good heat transfer therebetween. Passageways in the fin structure serve to conduct condensate from the heat exchanger While a wetting agent serves to facilitate condensate run-off.

The invention hereinabove described may be varied in construction within the scope of the claims, for the particular devioe selected to illustrate the invention is but one of many possible embodiments of the same. The invention, therefore, is not to be restricted to the precise details of the structure shown and described.

What is claimed is:

1. A heat exchange unit comprising a series of serpentine heat exchange tubes arranged in spaced parallel planes, each tube including a plurality of straight parallel conduits having integral U-bend connections at their ends; cellular fin structures disposed between adjacent ones of the tubes; each fin structure comprising connected walls extending normal to the tube planes, said fin structure walls having leading edges and trailing edges equipped with notches which mate with surface portions of the heat exchange tubes; successive tubes having their straight conduits offset in directions parallel to the tube planes, whereby fluid flowing between the straight conduits of one tube directly runs into the straight conduits in the succeeding tube.

2. A heat exchange unit comprising a series of heat exchange tubes arranged in spaced parallel planes, each tube including a plurality of connected straight parallel conduits; cellular fin structures disposed between adjacent ones of the tubes; each fin structure comprising connected sinuous Walls having faces thereof extending normal to the tube planes and defining hexagonal passages for flow of fluid normal to the tube planes; said fin structure walls having leading edges and trailing edges equipped with notches which mate with surface portions of the heat exchange tubes; successive heat exchange tubes having their straight conduits offset in directions parallel to the tube planes, whereby fluid flowing between the straight conduits of one tube directly runs into the straight conduits in the succeeding tube.

3. The heat exchange unit of claim 2 wherein the sinuous walls of successive fin structures are arranged crosswise of one another, whereby the leading edges of each fin structure are substantially completely exposed to the oncoming fluid.

4. A heat exchange unit comprising a series of heat exchange tubes arranged in spaced parallel planes, each tube including a plurality of connected straight parallel conduits; cellular fin structures disposed between adjacent ones of the tubes; each fin structure comprising connected sinuous walls extending normal to the tube planes and defining hexagonal fluid passages for directing fluid normal to the tube planes; said fin structure walls having leading edges and trailing edges equipped with notches which mate with surface portions of the heat exchange tubes, the notches in the trailing and leading edges of adjacent fin structures having combined depths which are less than the corresponding outside dimensions of the heat exchange tubes whereby adjacent fin structure edges are spaced from one another.

5. A heat exchange unit comprising a series of serpentine heat exchange tubes arranged in spaced parallel planes, each tube including a plurality of straight parallel conduits having integral U-bend connections at their ends; cellular fin structures disposed between adjacent ones of the tubes; each fin structure comprising connected sinuous walls having faces thereof extending normal to the tube planes and defining hexagonal fluid passages for flow of fluid normal to the tube planes; said fin structure walls having leading edges and trailing edges equipped with notches which mate with surface portions of the heat exchange tubes, the notches in the trailing and leading edges of adjacent fin structures hav ing combined depths which are less than the corresponding outside dimensions of the heat exchange tubes whereby adjacent fin structure edges are spaced from one another; successive heat exchange tubes having their straight conduits olfset in directions parallel to the tube planes, whereby fluid flowing between the straight conduits of one tube directly runs into the straight conduits in the succeeding tube; the sinuous walls of successive fin structures being arranged crosswise of one another, whereby the leading edges of each fin structure are freely exposed to the oncoming fluid.

References Oited by the Examiner UNITED STATES PATENTS Keegan 165-152 Still 165152 Huggins 29157.3 Bailey 165-133 X Baxter 29-1573 Huggins et al 165152 Simpelaar 165181 8 3,136,038 6/1964 Huggins et al 29157.3 3,147,800 9/1964 Tadewald 165--18l X FOREIGN PATENTS 5 246,371 12/1960 Australia.

361,558 6/1906 France. 379,652 4/1940 Italy.

OTHER REFERENCES 10 German Printed Application No. 1,129,975, 5/ 1962.

ROBERT A. OLEARY, Primary Examiner.

CHARLES SUKALO, Examiner. 

1. A HEAT EXCHANGE UNIT COMPRISING A SERIES OF SERPENTINE HEAT EXCHANGE TUBES ARRANGED IN SPACED PARALLEL PLANES, EACH TUBE INCLUDING A PLURALITY OF STRAIGHT PARALLEL CONDUITS HAVING INTEGRAL U-BEND CONNECTIONS AT THEIR ENDS; CELLULAR FIN STRUCTURES DISPOSED BETWEEN ADJACENT ONES OF THE TUBES; EACH FIN STRUCTURE COMPRISING CONNECTED WALLS EXTENDING NORMAL TO THE TUBE PLANES, SAID FIN STRUCTURE WALLS HAVING LEADING EDGES AND TRAILING EDGES EQUIPPED WITH NOTCHES WHICH MATE WITH SURFACE PORTIONS OF THE HEAT EXCHANGE TUBES; SUCCESSIVE TUBES HAVING THEIR STRAIGHT CONDUITS OFFSET IN DIRECTIONS PARALLEL TO THE TUBE PLANES, WHEREBY FLUID FLOWING BETWEEN THE STRAIGHT CONDUITS OF ONE TUBE DIRCTELY RUNS INTO THE STRAIGHT CONDUITS IN THE SUCCEEDING TUBE. 